Fatal thoracic aortic transection following a motor vehicle collision: Medico-legal significance of the seat belt sign.

Traumatic thoracic aortic transection is one of the most lethal consequences of blunt chest trauma; it is commonly associated with high-speed deceleration injuries in road traffic collisions. Despite advances in trauma management, survival rates remain poor due to rapid internal haemorrhage and the presence of multiple associated injuries. We report a fatal case of thoracic aortic transection in a 50-year-old restrained male driver involved in a high-velocity head-on collision with a truck. Following admission, he presented with hypotension, left-sided flail chest, multiple long bone fractures and reduced consciousness. Although emergency resuscitation was initiated, he developed sudden cardiovascular collapse during radiological evaluation and could not be revived. Medico-legal autopsy revealed a patterned seat belt contusion across the anterior chest wall, multiple rib fractures, extensive mediastinal haemorrhage, left-sided haemothorax and a circumferential full-thickness transection of the proximal descending thoracic aorta distal to the left subclavian artery. Toxicological analysis detected alcohol and morphine. This case highlights the characteristic pathological features of traumatic thoracic aortic injury and emphasises the medico-legal significance of the seat belt sign in identifying severe underlying thoracic trauma and reconstructing fatal motor vehicle collisions.